• Mass Spectrometry Letters
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• v.8 no.3
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• pp.65-68
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• 2017

Thiamethoxam is one of the main suspect in honeybee colony collapse disorder (CCD). Due to this reason, thiamethoxam including imidacloprid and clothianidin has been banned for two years in some Europe countries. The CCD phenomenon has also been reported in Korea. Regarding this issue and needs, a new project has started to develop the method for the quatitation of thiamethoxam using isotope dilution mass spectrometry (IDMS). In the process of optimization for the IDMS method with thiamethoxam and $thiamethoxam-d_3$, we observed that the fragment peaks did not correspond to the fragmentation pathway as published elsewhere. Here, we proposed a candidate fragmentation pathway. To validate the proposed fragmentation pathway, another isotope analogue, $thiamethoxam-d_4$, was introduced and the MS/MS spectra of both isotope analogues were compared. In addition, the MS/MS/MS spectra of thiamethoxam were inspected for more evidence of the candidate pathway. Those spectra indicated that the proposed fragmentation pathway could be used to assign the fragment peaks of thiamethoxam.

• Korean Journal of Environmental Agriculture
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• v.41 no.4
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• pp.355-364
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• 2022

BACKGROUND: Pre-harvest interval and decline pattern of thiamethoxam were determined in kiwifruit using liquid chromatography-tandem mass spectrometry (LCMS/MS). The study was carried out to propose import tolerance using OECD maximum residue limit (MRL) calculator for the export promotion of kiwifruit to Taiwan. METHODS AND RESULTS: The thiamethoxam residue in kiwifruit was determined by using the LC-TriQ-MS/MS with the analytical process to set up the import tolerance under greenhouse conditions for Taiwan. Excellent linearity was observed for all of the analytes with a determination coefficient (R²)≥0.99. The limit of quantification was determined to be 0.01 mg/kg for both thiamethoxam and clothianidin in kiwifruit. Linearity was determined from the co-efficient of determinants (R²) obtained from the seven-point calibration curve. The standard calibration curve showed as follows; 1) Site 1 (Gimje): y = 944,406X + 1,583 (R²=0.9995), 2) Site 2 (Goheung): y = 1,356,205X + 934 (R²=0.9983), and 3) Site 3 (Jangheung): y = 1,239,937X - 3,090 (R²=0.9908). The residue of thiamethoxam in the kiwifruit for three decline trials showed the range of 0.35 to 0.56 mg/kg in site 1 (Gimje), 0.24 to 0.55 mg/kg in site 2 (Goheung), and 0.28 to 0.42 mg/kg in site 3 (Jangheung), respectively. However, clothianidin was not detected in all of the treatments. The maximum residual amounts (decline) in the samples, sprayed according to the safe-use standard for thiamethoxam 10% WG in kiwifruit (30 days before harvest, 3 sprays every 7 days) were 0.56 mg/kg in site 1, 0.55 mg/kg in site 2, and 0.42 mg/kg in site 3, respectively. CONCLUSION(S): The import tolerance (IT) of thiamethoxam for kiwifruit may be proposed to be 0.9 mg/kg by using the OECD MRL calculator.

• The Korean Journal of Pesticide Science
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• v.6 no.4
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• pp.244-249
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• 2002

This study was carried out to investigate the toxicities of 22 insecticides to Dichromothrips smithi. Insecticidal activity was evaluated by testing systemic action and residual effect in laboratory. All insecticides used in this study did not affect on the egg of D. smithi, although organophosphates such as fenitrothion, fenthion, methidathion, phenthoate, and phenthoate+ethofenprox suppressed the egg hatchability completely. On D. smithi larva fenitrothion, fenthion, methidathion, phenthoate, ethofenprox, thiamethoxam, abamectin, chlorfenapyr, emamectin benzoate, fipronil, spinosad, and phenthoate+ethofenprox showed 100% insecticidal activity. On D. smithi adult fenitrothion, fenthion, methidathion, phenthoate, ethofenprox, abamectin, emamectin benzoate, fipronil, spinosad, and phenthoate+ethofenprox showed 100% insecticidal activity. Root-uptake systemic effects of phenthoate on the larva of D. smithi was 43.3%. Whereas, systemic effect of other insecticides was less than 20%. Insecticide with more than 80% residual effect for 7 days after treatment were fenitrothion, fenthion, methidathion, phenthoate, ethofenprox, emamectin benzoate, fipronil, spinosad, and phenthoate.

• Korean journal of applied entomology
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• v.56 no.4
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• pp.427-434
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• 2017

The susceptibility of Dermanyssus gallinae adults, collected from poultry farms in 5 regions, to 11 acaricides was investigated. When bifenthrin and formic acid with pyridaben were diluted 100 times, bifenthrin showed 100% acaricidal activity; however, formic acid with pyridaben showed less than 20% acaricidal activity for poultry farms in 3 regions (Gyeongju, Chilgok, and Geumsan) except Yeoncheon and Anseong. The carbamate compound, carbaryl showed 100% acaricidal activity in most of the regions, except Gyeongju. A phosphorus compound, dichlorvos showed 100% activity in most of the regions, yet 66.7% acaricidal activity in Yeoncheon. The susceptibility of D. gallinae from poultry farms in Yeoncheon and Anseong to most acaricides was high; however, in the other farms, the susceptibility of D. gallinae varied depending on the acaricide. Clothianidin, thiamethoxam, fenitrothion, and formic acid with pyridaben showed differences in acaricidal activity among regions. Therefore, farmers should concentrate during the selection of these acaricides. However, carbaryl, cartap hydrochloride, dichlorvos, and bifenthrin showed high activity against D. gallinae collected from poultry farms in five regions. Therefore, these acaricides could be used in most of these regions. To control D. gallinae effectively, the alternation of acaricides is necessary, and indiscriminate pesticide use should be avoided. Therefore, this study can serve as a basis for controlling D. gallinae.

• Journal of Korean Society of Forest Science
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• v.89 no.3
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• pp.384-388
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• 2000

For the control of Corythucha ciliata, the insecticidal activity of five commercial pesticides (Monocrotophos 25%SL, Phosphamidon 50%SL, Imidacloprid 20%DC, Thiamethoxam 15%DC and Acetamiprid 20%SL) were examined with trunk injection method in Seoul, Sanbon and Chungju. The insecticidal activity of five commercial pesticides was >88%. The insecticidal activity of Monocrotophos maintained 31 days later after trunk injection when treated leaves were supplied to this pest. This result indicates that one application of trunk injection is enough to control this pest, and this method can save the control cost compared with ground application which should be applied two or three times per year to control this pest. To make the model of treatment dosage at each D.B.H class (cm), $1.0m{\ell}/DBH$, $1.5m{\ell}/DBH$ and $2.0m{\ell}/DBH$ pesticide dosage was used. At <20cm, the insecticidal activity of $1.0m{\ell}$ dosage was >95%, and $1.5-2.5m{\ell}$ dosage was needed for the effective control at 30~50cm. More than $2.5m{\ell}$ dosage was effective at >50cm. Spray method was used in laboratory to select pesticides for ground application. Three commercial pesticides (Ethofenprox 20%EC, Ethofenprox 10%WP and Cyfluthrin 1%EC) were used, and all pesticides showed >95% insecticidal activity.

• The Korean Journal of Pesticide Science
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• v.5 no.1
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• pp.55-60
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• 2001

The efficacy of petroleum spray oil (PSO; D-C Tron $Plus^{(R)}$) against spirea aphid (Aphis citricola) and two scales (lcerya purchasi and Planococcus cryptus) on citrus was tested in Jeju, Korea. The control value of 0.33% PSO against spirea aphid was over 90% at 3 and 6 days after treatment (DAT), and then decreased to about 80% at 9 and 14 DAT. Spraying of PSO (0.33, 0.66, 1%) against cottony-cushion scale showed a much lower control value (less than 50%) during the investigation period compared to that of the conventional pesticide (Methion). When used against tile scale, Planococcus cryptus, the control value of 1% PSO was 95%, but that of 0.33% and 0.66% PSO only ranged from 50 to 80%, lower than the conventional pesticide. The results of this study, as with a previous study, suggest that spraying of 0.33% and 0.5% PSO not only controls the spirea aphid, but also reduces the density of two scales (lcerya purchasi and Planococcus cryptus) on citrus tree in Jeju, without phytotoxic damage.

• The Korean Journal of Pesticide Science
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• v.15 no.1
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• pp.15-21
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• 2011

Monitoring or follow-up surveying pesticide residues in agricultural commodities is the key to meet the international regulations and to enhance international competitiveness of Korean agricultural commodities. Six neonicotinoid insecticides, acctamiprid, clothianidin, dinotefuran, imidacloprid, thiacloprid, and thiamethoxam were monitored in 95 paprika samples collected from Gyeongnam area. Thc pesticide residues were extracted by EN 15662 buffer based on the QuEChERS method, clean-upped with dispersive solid-phase extraction method to remove interfering pigments, and analyzed using UPLC-MS/MS. The neonicotinoid pesticides were detected in 90.5% of the paprika samples. Two or more pesticides were detected in 82.3% of samples. Although detection frequencies were high, all samples complied with the maximum residue limits (MRLs) set by both the Korea Food and Drug Administration (KFDA) and Japanese Ministry of Health, Labour and Welfare.